Gear gauging apparatus



1957 T. s. GATES GEAR GAUGING APPARATUS Eilec 1-Sept. 12, 1955" 2Sheets-Sheet 1 -INVENTOR.

THOMAS S GATES ATTORNEYS T.S.GATES Filed Sept. 12. 1955 TO M 2Sheets-Sheet 2 INVENTOR. THOMAS s. GATES 'ATTORNE S United States PatentGEAR GAUGING APPARATUS Thomas S. Gates, Grosse Pointe Woods, Mich,assignor to National Broach & Machine Company, Detroit, Mich, acorporation of Michigan Application September 12, 1955, Serial No.533,619 6 Claims. (Cl. 209-88) The present invention relates to geargauging apparatus, and more particularly, to automatically operatedgauging apparatus effective to determine a minimum predetermineddeviation from a plurality of standard gear conditions and to separategears into a plurality of groups in a fully automatic operation, thegroups comprising acceptable gears, gears which are unacceptable butwhich are capable of being salvaged, and unacceptable gears which arenot capable of being salvaged or scrap gears.

The present invention is an improvement over the invention disclosed inmy prior application Serial No. 466,118 entitled Automatic Gear GaugingDevice, filed November 1, 1954.

t is an object of the present invention to provide gear gaugingapparatus including means movable in two different directions inaccordance with two different gear characteristics, and means forpreventing movement in one direction until a predetermined minimummovement has taken place in the other direction to insure propersequence of sensing of gear errors.

More particularly, it is an object of the present invention to providegear gauging apparatus comprising an arm movable about a first axis inaccordance with the size of a gear being gauged and movable about asecond axis perpendicular to the first axis in accordance with the helixangle of the teeth on the gears being gauged, limit switches actuated bymovement of the arm about either of said axes, and means for preventingsubstantial swinging movement of said arm about one of said axes untilit has moved a predetermined minimum distance about the other of saidaxes.

Still more specifically, it is an object of the present invention toprovide gear gauging apparatus comprising an arm movable from a restposition through a first range of positions corresponding to slightlyundersize condition of a gear, through a second range of positionscorresponding to acceptable dimensions of a gear, and

into a third range of positions corresponding to slightly oversizecondition of a gear; and movable about a second axis perpendicular tothe first axis from an intermediate range of positions corresponding toacceptable helix angle of a gear to either side of such range in accord-;ance with unacceptable right and left hand deviation in gear helixangle, three limit switches, one or more of which is adapted to beactuated sequentially by said arm upon movement from rest position aboutthe first axis toward the third range of positions, a pair of limitswitches adapted to be actuated alternately by movement of said armabout said second axis in both direc tions out of the acceptable rangeof helix angle, gear selecting mechanism to separate a series of gearsinto acceptable gears, salvageable gears, and scrap gears, and means forpreventing actuation of either of said pair of limit switches at leastuntil the first of said three limit switches has been actuated.

It is a further object of the present invention to provide 2,393,342Patented Aug. 20, 1957 gear gauging apparatus comprising one or moremaster gears adapted to be meshed with a gear to be gauged, at least oneof said master gears having its teeth modified longitudinally andpreferably crowned to eliminate or minimize the effect of helix angle ortaper error in gang ing size. v I

Other objects and features of the invention will become apparent as thedescription proceeds, especially when taken in conjunction with theaccompanying draw ings, wherein: Y

Figure 1 is a more or less diagrammatic elevational view of gear gaugingapparatus constructed in accordance with the present invention.

Figure 2 is a developed sectional View through a meshing master gear andwork gear developed into a plane.

Figure 3 is a fragmentary sectional view on the line 3-3, Figure 1.

Figure 4 is a wiring diagram of electrical equipment associated with themechanism shown in Figure 1.

The gear gauging apparatus disclosed in Figure 1 is intended to gauge aseries of gears as finished by a gear finishing operation, such forexample as a gear shaving operation. Alternatively, the same mechanismmay be employed for gauging a series of gears in a fully automaticoperation as the gears are advanced into a machine for shaving thegears. In order to control the sequence of gauging in an orderly manner,a stop gate may be provided which admits the gears one at a time to thegauging apparatus. This gate may conveniently be under the control of asolenoid actuated by exit from the gauging apparatus of the gearpreviously gauged. Since the gauge may be used to shut down the shavingmachine, it is desirable that gears be gauged substantially as they arefinished by the machine.

The gauging apparatus comprises a pair of master gears 1d and 12, thegear 19 being mounted on a shaft 14. Preferably, suitable motor means(not shown) is connected to the shaft 14 to drive the gear 10 in acounterclockwise direction as seen in Figure 1, to advance gearsautomatically into the apparatus and through the space between mastergears 10 and 12.

The master gear 12 is located adjacent the master gear 10 with its axisgenerally parallel thereto, thereby providing a space between the mastergears 10 and 12 through which a series of gears to be checked or gaugedare passed. The master gear 12 is journaled between parts 16 at the endof a gooseneck 18 provided on a relatively long measuring or gauging arm20 which preferably is formed of a cast light metal such for example asaluminum or magnesium. The purpose of providing the long arm 20 is tomagnify or amplify movement of the master gear 12 resulting from passageof a work gear between master gears 10 and 12. The arm 20 is journaledfor angularhmovement about the axis of a pivot shaft 22, the ends of theshaft 22 being received in bearings as indicated at 2 4 and 26, thebearings being received in a bracket 28 which in turn is mounted forrocking movement about a pivot pin 30 carried by a stationary mountingbracket 32. As a result of the foregoing construction the gauging arm 20is movable to gether with bracket 28 about the axis of the pivot pin 30and is movable relative to the bracket 28 about the axis of the pivotpin 22.

The master gear 12 is rotat'ably mounted on a pivot pin 34 but is heldagainst rotation by a plug of soft material pressed against theperiphery thereof by a screw 40. By loosening the screw 40, the mastergear 12 may be slightly rotated to present a diiferent portion of itsperiphery to gears being gauged.

The gears to be checked are led to the gear gauging apparatus along asuitable chute or trackway, a portion of which is indicated at 42 whencethe gears pass to a surface 44 along which they rollinto engagement withthe rotating or driving master gear 10. As the gear to be gauged engagesthe master gear 10, it may or may not in the first instance becomemeshed therewith and a plate 46 having a nose portion 48 is providedwhich prevents the gear being gauged from contacting the upper mastergear 12 until it has become fully meshed with the lower rotating master.gear.

As the gear to be gauged passes through the space between'the mastergears and 12, the teeth of the master gear 12 will enter into the spacesin the gear being gauged and the arm will be swung about the axis of theshaft to a point determined by the pitch diameter of the gear beinggauged. At the same time, or in suitably timed relation as willsubsequently appear, the arm 20 will be swung about the axis of theshaft 22 in accordance with any right or left hand helix angle errorpresent in the gear being gauged;

After the gear has passed through the space between the master gears10and 12 it drops to a surface 50 and thence rolls downwardly and to theleft over trap doors 52 and 54, and thence drops off the trackway to aconveyor or receptacle for receiving gears within acceptable limits asto size and helix angle. As will subsequently appear, either of the trapdoors 52 or 54 may be projected into an open position in which theyblock passage of the gauged gear and cause it to drop down to a conveyoror receptacle for the reception of rejected gears.

The arm 20 has connected thereto a tension spring 56 the upper end ofwhich is connected to an adjustable screw 58. The spring 56 biases thearm 20 clockwise as' seen in Figure 1, to a position in which anabutment 60 thereon engages anadjustable abutment and timing screw 62carried by a post 64. Adjustment of the screw 62 predetermines theposition of the master gear 12 prior to engagement therewith of a gearbeing gauged. This adjustment is normally such that passage of even anabnormally undersize gear will result in counterclockwise movement ofthe arm 20 as seen in Figure 1. In other words, the illustrated positionof the arm 20 may be referred to as under under-size; that is, aposition from which it will 'be displaced by passage of the smallestundersize gear expected to be within the lot gauged.

Associated with the arm 20 and cooperating therewith to sense or measuresize of the gear being gauged are limit switches LS1, LS2 and LS3, theseswitches having plungers indicated generally at 66, actuated byadjustment screws 68 on the arm 20. The arrangement is such that as agear having a pitch diameter or size such as to be unacceptable asundersize passes between master gears 10 and 12, the arm 20 is swungclockwise an amount sufficient to actuate limit switch LS1. If the gearis of acceptable size arm 20 will be swung slightly further so as toactuate limit switch LS2. If the gear is unacceptable as a result ofbeing over size, arm 20 will be swung still further to a position toactuate limit switch LS3.

In addition, limit switches LS4 and LS6 are provided and adapted to beactuated by the arm 20 as it is swung about the axis of pivot pin 22.Specifically, limit switch LS4 is in a position tobe actuated when thearm 20 is swung as a result of a left hand helix angle error ofunacceptable magnitude, and limit switch LS6 is in position to beactuated by arm 20 when it is moved as a result of a right hand helixangle error in a gear being gauged of unacceptable magnitude.

Means are provided for actuating the trap doors 52 and 54 andthese meanscomprise solenoids A and B respectively. The trap doors 52 and 54 arecarried by pivot pins 70 having cranks 72 connected thereto, the cranksbeing connected by links 74 to the plungers 76 of the solenoids. Thearrangement is such that Whenthe solenoids A or B are energized the trapdoors are swung upwardly, leaving openings through which the gaugedgears may descend. The trap doors in the raised position also formbarriers to insure passage of the gear through the opening and toprevent further passage of the gear along the trackway.

The trap doors 52 and 54 each cover an escape exit for gauged gears andgears which pass both trap doors roll off the end of the trackway 'aspreviously described. In order to provide means which sense the movementof a gear downwardly through a space vacated by a trap door or cross thespace at the end of the trackway, identical means are provided. Thesemeans comprise levers 80 mounted for rocking movement by pivot pins 82and having lower end portions in position to be engaged by a gearpassing out of the gauging apparatus. At their upper ends each of thelevers 80 includes an adjustable switch actuating screw 84 and these areadapted to actuate limit switches LS7, LS8 and LS9. Spring means 86 isprovided biasing the levers 80 into position to clear the associatedlimit switches and to be in the path of movement of the gears out of thegauging apparatus.

In general, the arrangement is such that as a gear passes between themaster gears 10 and 12, the arm 20 is swung so as to actuate one or moreof the limit switches LS1, LS2 and LS3, and to actuate one of the limitswitches LS4 or LS6 if the gear has too great a helix angle error.Dependent upon which of these limit switches have been actuated, one ofthe trap doors 52 or 54 may be raised or both may remain closed. In anycase a gear passing out of the gear gauging apparatus will actuate oneof the limit switches LS7, LS8 or LS9, giving a signal that theapparatus has cleared the gear and is ready to receive the next gear fora gauging operation.

As will appear from the description of the wiring diagram, an under sizegear, which cannot be salvaged, will actuate limit switch LS1 and thisin turn will actuate solenoid A so that by a circuit later to bedescribed trap door 52 is raised and this scrap gear will be ejecteddownwardly through the space vacated by the trap door 52. If the gear isoversize or is unacceptable as a result of having a helix angle error,it may be salvaged and will actuate limit switch LS3 and/ or LS4 or LS6,thus raising trap door 54 and permitting this salvageable gear to passto a different chute or receptacle.

If the gear is acceptable both as to size and helix angle limit switchesLS1 and LS2 only will be actuated and the gear will pass over both ofthe trap doors 52 and 54 and will pass to a third chute or receptacledesignated for acceptable gears.

Referring now to Figure 4, there is illustrated the circuitinterconnecting the various limit switches and solenoids previouslyreferred to. The circuit includes lines L1 and L2 connected through aswitch SW1 and thermal overload device TO to lines Lla and L2arespectively. Connected across the switch SW1 is a motor M controlled bycontacts Mla of a master relay M1. Extending between lines Lla and L2ais a stop switch SW2, the contacts of a start-reset switch SW3, and themaster relay M1. 'Normally open contacts M1b of the relay M1 areconnected around the start contacts of the switch SW3 and a signal lightSL is connected in parallel with the 7 master relay M1.

From the foregoing it will be apparent that when the start-reset switchSW3 is depressed into engagement with the lower pair of contacts, acircuit is completed through the stop switch SW2 and the master relayM1. Energization of the relay M1 closes normally open contacts Mla, thusengaging the motor M and also closing normally open contacts Mlb andM10. Closure of contacts Mlb establishes a holding circuit around thelower pair of contacts of the start-reset switch SW3, and closure of thecontacts M10 energizes the circuit to the various limit switches as willnow be described.

It will be recalled that condition limit switches LS1, LS2 and LS3 areadapted to be actuated in sequence as .a gear passes through the spacebetween master gears 10 and 12 if the'gear is oversize. An undersizegear actuates limit switch LS1. If the gear is of the required sizelimit switches LS1 and LS2 are actuated in sequence but limit switch LS3is not actuated. Limit switch LS1 is provided with two sets of contactsand will move from the illustrated position to the lower position uponinitial movement of the arm 20. This completes a circuit from line L2ato line L141 through normally closed relay contacts R2b, R311, R7a torelay R1. Energization of relay R1 closes normally open contacts R10,thus establishing a holding circuit for the relay R1 independent ofcondition limit switch LS1. In addition, energization of the relay R1also closes normally open contacts R1]; and Rld and opens normallyclosed contacts Rlc.

Condition limit switch LS2 is connected between lines L2a and Lla inseries with normally closed contacts R30, R7b and relay R2. Relay R2when energized closes normally open contacts R2a establishing a holdingcircuit around limit switch LS2. In addition, energization of relay R2closes normally open contacts RZc and opens normally closed contactsR21) R1, thus de-energizing relay R1.

Condition limit switch LS3 is also connected between lines L2a and Llaand is in series with normally closed contacts R70 of relay R7 and withrelay R3. Energization of relay R3 closes normally open contacts R311,establishing a holding circuit around limit switch LS3, and opensnormally closed contacts R322 and R30, thus breaking the circuit torelay R2. The circuit to relay R1 was previously broken by closure oflimit switch LS2. Normally open contacts RM and R3e are also closed byenergization of relay R3.

With the three branch circuits including relays R1, R2 and R3, it willbe observed that initial movement of the arm 29 operates condition limitswitch LS1 from the position shown and will energize relay R1. Furthermovement of the arm 20 operates condition limit switch LS2 which willde-energize relay R1. Still further movement of the arm 20 will operatecondition limit switch LS3 to energize relay R3 which will de-energizerelay R2. Accordingly, if an undersize gear passes between the mastergears 10 and 12, relay R1 becomes and remains energized. If a normalsize gear passes between the master gears, relay R1 is energized andde-energized when relay R2 is energized. Relay R3 is not energized. Ifan oversize gear passes between the master gears relay R3 becomes andremains energized and relays R1 and R2 are de-energized. From thisstandpoint it will be appreciated that condition limit switches LS1, LS2and LS3 cooperate to control the gauging apparatus in accordance withthe size of the gear, limit switch LS1 having the additional function ofdelaying operation of the solenoids until the gear being gauged haspassed the master gears.

In a similar manner, condition limit switches LS4 and LS6 are responsiveto helix angle error, each being connected in series with relays R4 andR6 respectively. The circuit including the relay R4 includes normallyclosed contacts R511, R612 and R741. The circuit including the relay R6includes normally closed contacts R71. Limit switches LS4 and LS6 areeach provided with holding contacts R451 and such that if the gearexhibits elf-helix angle to the left limit switch LS4 energizes relayR4, closing normally open contacts R4a, R412 and R42. In like manner, iflimit switch LS6 is closed, energization of relay R6 closes normallyopen relay contacts R651, Rh'd' and R69 and opens normally closedcontacts R615.

In addition to the limit switches so far described, limit switches LS7and LS9 are connected in parallel with each other between the lines L211and L10. The two limit switches are in series with relay R7. Thearrangement is such that closure of either limit switch LS7 or LS9energizes relay R7. Energization of relay R7 opens normally closed relaycontacts R7a, R7b, R7c, R7d and R77. In addition, limit switch LS8 is inseries with relay in series with the relay Rea respectively. Thearrangement is R5 and closure of limit switch LS8 closes normally openrelay contacts R5a which are in parallel with the contacts of both limitswitches LS7 and LS9.

It will be recalled that limit switches LS7, LS8 and LS9 are actuated bypassage of a gear through any one of the three escape paths. Closure oflimit switch LS8, energizing relay R5, closes relay contacts RSa andtherefore has the same effect as closure of limit switches LS7 or LS9 inenergizing relay R7. Relay R8 is provided which is adapted to enter intoan additional circuit for the purpose of counting rejected gears.

If an undersize gear passes through the machine it will have actuatedonly limit switch LS1 and this will have energized relay R1, closingnormally open contact Rld. This contact is in series with solenoid A.Accordingly, a circuit will beprepared for subsequent energizationextending from the upper contacts of limit switch LS1 through normally Yopen but now closed contact Rld. When the gear has passed through thespace between the master gears, limit switch LS1 will return to theillustrated position, thus completing a circuit to the solenoid A whichwill remain energized and will hold trap door 52 open. The gauged gearwill thus pass through the opening vacated by the trap door 52 and willengage the associated lever 89, thus closing limit switch LS7. Closureof limit switch LS7 momentarily ener izes relay R7 which in turn opensall of the normally closed contacts R7a, R7b, R7c, R7d and R77, and thusin turn de-energizing any of the relays R1, R2, R3, R4 or R6 which areat that time energized. This in turn opens normally open contacts Rld,de-energizing solenoid A and permitting trap door 52 to close.

If on the other hand, the gear is of proper size so that the limitswitch LS2 remains closed, thus maintaining relay R2 closed, but isoff-angle with a right hand helix angle error, limit switch LS6 isclosed energizing relay R6 and closing normally open contacts R62. Atthis time relay R1 has opened as a result of closure of limit switch LS2and accordingly, normally closed contacts R10 are closed and a circuitis set up through contacts R10 and R62 to solenoid B. This circuit iscompleted when limit switch LS1 returns to the illustrated positionafter passage of a gear through the master gears. Energization ofsolenoid B of course lifts trap door 54 and the gear, which issalvageable as a result of having its teeth offangle, thus falls into achute or receptacle designated for the reception or" salvageable gears.It will be apparent of course that a similar result is obtained whenlimit switch LS3 or LS6 is closed since this will result in closure ofnormally open contacts R3e or R62, which are in parallel with contactsR42.

From the foregoing it is to be observed that limit switch LS1 preparesthe circuit for further operation and accordingly, it is essential thatlimit switch LS1 move to the lower position before either of the helixangle error detecting limit switches LS4 or LS6 is energized. This isalso an essential since it is required to separate undersize gears, assensed by limit switch LS1 from gears which are oversize as sensed bylimit switch LS3, off-angle to the left as sensed by limit switch LS4,or oil-angle to theright as sensed by limit switch LS6.

In order to insure the proper sequence in actuation of the limitswitches, and at the same time to avoid introduction of errors byimposing substantial forces on the delicate mechanism, the block 60which with the adjustable screw 62 constitutes the abutment limiting theidle position of the gauging arm 20, is formed as illustrated in Figure3. It will be observed that the nose of the adjustable screw 62 isrounded off or tapered as indicated at 9% and the block 60 is providedwith a centering notch of U-shape as indicated at 92. Accordingly, whena' gear passes through the space between the master gears 10 and 12, thespring 56 biases the gauging arm 20 clockwise. Engagement between thetapered nose 90 of the screw 62 and the V-shaped notch in the abutment60' causes the arm to become centered between helix angle error sensinglimit switches LS4 and LS6. Moreover, the sides of the notch 92 and thenose of the screw 62 are so shaped that lateral movement of the arm 20is restricted to an amount insufficient to operate either of the limitswitches LS4 or LS6 until after the arm has moved sufficiently toactuate limit switch LS1.

With this arrangement the arm is substantially free to move laterallybut such movement is prevented until after limit switch LS1 has beenactuated.

A further improvement in the gauging apparatus comprises providing theteeth of one or both of the master gears 10 or 12 with longitudinalmodification to produce certain desired results. A preferred form of theinvention is diagrammatically illustrated in Figure 2 which may beconsidered as a sectional view taken on the pitch cylinders of twomeshing gears and then developed into a single plane. Ta represents theteeth of the gear being gauged and Tb represents longitudinally convexlycrowned teeth of a master gear.

It will be appreciated that if the arm 24 is prevented from oscillatingabout the axis of the shaft 22, the apparatus'may operate to gauge thesize of a gear passed between the master gears 10 and 12. However, inthis case, if the teeth of the master gear are off-lead, the teethwillnot mesh to full depth with the teeth of the master gears, andaccordingly, the apparatus will give an indication of an oversize gear.Similarly, if the teeth of the gear being gauged are tapered so as to belarger at one end than the other, they will mesh to full depth only atone end and this will also give an indication of being oversize.Aocordingly, an oversize gear, which in addition has teeth extending atan oil-lead condition and which are in addition tapered, will beindicated merely as overslze.

In order to eliminate the false portion of the oversize indicationresulting from ofi-lead and/or tapered teeth,

the teeth of the master gear or master gears may be crownedlongitudinally so as to have the theoretical perfect tooth thicknessonly at the center. In this case the master gear will contact taperedteeth only adjacent the cener and will also mesh to substantially fulldepth with oft-lead teeth so that the size indication shown by the gaugewill be a true indication of size and will not inelude errorsattributable to lead or taper errors.

It is recognized that in some cases a composite check may be desired inwhich case teeth of the master gear will not be crowned, and anindication will result which is dependent upon size, helix angle, and atapered condi- &

tion. It will also be appreciated that if the teeth of the gear beinggauged are themselves crowned, it will be undesirable to provide crownedteeth on the master gear or master gears.

A second longitudinal tooth modification which is desirable in thepresent apparatus is in the case where the arm 20 is mounted foroscillation about mutually perpendicular axes so as to provide nominalsize and helix angle checks at the same time. In this case, if the teethof the gear to be checked are crowned, the contact between the teeth ofthe work gear and the teeth of the master gear 12 will be limited tosubstantially point contacts one at each side of each tooth, andaccordingly, insufiicient torque may be developed to swing the arm 29about the axis of pivot shaft 22. In order to overcome this difficultyit is desirable to provide longitudinally hollow or reverse crownedteeth on the master gear or master gears, in an amount to substantiallyconform to the crown of the teeth on the work gear. In this case contactof theoretically correct teeth will be line contact from end to end ofthe gear teeth and from end to end of the teeth of the master gear 12.If however, an off-lead condition exists, contact between the teeth ofthe work gear and the master gear 12 will be at opposite ends of theteeth of the master gear 12 so that suflicient torque is developed toswing arm 8, 20 about the axis of shaft 22, and thus to provide a trueindication of gear error. I p

In general, it may be said that if the apparatus is designed so that thearm 20 oscillates aboutthe axis of shafts 22 and 30, it is desirable toemploy a master gear or master gears having a crown or reverse crownmatching the crown or reverse crown on the teeth of the gear to bechecked, so as to develop sufficient torque to provide a true indicationof helix error. On the other hand, it the apparatus is employed in sucha way as to prevent oscilla tion of the arm 20 about the axis of theshaft 22, the teeth of the master gear or master gears may be crowned ifit is desired to obtain a substantially true indication of sizeunaffected by helix angle or taper error. If on the other hand, acomposite reading is desired which represents the accumulation of size,helix and taper error, the crowned teeth will not be employed on themaster gear or master gears.

- g The drawings and the foregoing specification constitute adescription of the improved gear gauging apparatus in such full, clear,concise and exact terms as to enable any person skilled in the art topractice the invention, the scope of which is indicated by the appendedclaims.

What I claim as my invention is:-

1. Gear checking apparatus comprising a moveable arm movable about afirst axis from a rest position corresponding to a gear sizesubstantially below any gear of a series to be checked through a firstrange of size positions corresponding to undersize gears, through asecond range of size positions corresponding to acceptable gear sizes,and into a third range of size positions corresponding to oversizegears, said arm being movable about a second axis perpendicular to saidfirst axis from a first range of angle positions correspondingto gearsacceptable as to helix angle in either direction into two ranges ofangle positions corresponding to gears unacceptable because of helixangle errors, means effective when no gear is being gauged to returnsaid arm to said rest position, and guide means effective to locate saidarm within said first range of angle positions while at said restposition.

2. Apparatus as defined in claim 1 comprising means for separatingrejected gears according to size and angle error, said means comprisinga first switch operated by said arm upon movement into said first rangeof size positions, a pair of switches one of which is operated bymovement of said arm from said first range of angle positions to eitherof said two ranges of angle positions.

3. Apparatus as defined in claim 2, said guide means eing shaped toprevent movement of said arm about said second axis of sufiicientmagnitude to actuate either of said pair of switches until said arm hasmoved about said first axis from rest position into said first range ofsize positions.

4. Apparatus as defined in claim 1, said guide means comprising aV-shaped notch adjacent said arm, and

means on said arm movable into said notch, the angle between the sidesof said notch being selected to prevent actuation of either of said pairof switches before actuation of said first switch upon passage of a gearthrough the apparatus.

5. Gear gauging apparatus comprising means for moving a series of gearsto be gauged through fully meshed engagement with two master gears, amovable arm on wh1ch one of said master gears is mounted, pivot meansmounting said arm for rocking movement in a direction to move the mastergear carried thereby substantially radially toward and away from a gearto be gauged, indicating mechanism associated with said arm adapted tomeasure the size of the gear, the teeth of one of said master gearsbeing longitudinally crowned so as to provide clearance between the endsof the teeth of the gear being gauged and the teeth of the master gearand to limit contact therebetween to a zone located substantiallyinwardly from the ends of the teeth of the gear being gauged.

6. Gear gauging apparatus comprising means for moving a series of gearsto be gauged through fully meshed engagement with two master gears, amovable arm on which one of said master gears is mounted, pivot meansmounting said arm for rocking movement in a direction to move the mastergear carried thereby substantially radially toward and away from a gearto be gauged, indicating mechanism associated with said arm adapted tomeasure the size of the gear, the teeth of both of said master gearsbeing longitudinally crowned so as to provide clearance between the endsof the teeth of the gear being gauged and the teeth of the master gearand to limit contact therebetween to a zone located substantiallyinwardly from the ends of the teeth of the gear being gauged.

19 References Cited in the file of this patent UNITED STATES PATENTSLorenz Feb. 20, 1951 Pomernacki Sept. 4, 1956 OTHER REFERENCES

